Hungry Black Hole

A black hole about 20,000 times as massive as the Sun may inhabit a star cluster indicated by the small circle on the outskirts of the galaxy ESO 243-49. The intermediate-mass black hole -- one of the few yet detected -- appears to be taking a bite out of an orbiting star about once every year, when the star comes closest to the black hole. The cluster could be the leftover core of a smaller galaxy that has been taken over by ESO 243-49. Intermediate-mass black holes, which are larger than those that form from the collapse of stars but smaller than those in the hearts of most galaxies, have been hypothesized, but only a few possible examples have been detected. The black hole is designated ESO 243-49 HLX-1, which indicates that it is the first "hyperluminous X-ray object" discovered in the galaxy. We have more details about ESO 243-49 HLX-1[4] in our Black Hole Encyclopedia[5]. [NASA/ESA/S. Farrell (University of Sydney)]

One of the last remnants of a dead galaxy — a medium-sized black hole — may be devouring a companion star, taking a bite when the star comes close every year or so. As the black hole swallows the stolen gas, it flares brightly, producing an outburst of X-rays that slowly fades — until the next bite.

The object is known as ESO 243-49 HLX-1. It orbits a large spiral galaxy that’s almost 300 million light-years away.

HLX-1 was discovered in observations by an X-ray telescope in space. The X-rays suggested the object was a disk of superhot gas around a black hole. Follow-up observations allowed astronomers to measure the mass of the central black hole: about 20,000 times the mass of the Sun — one of only a handful of possible black holes of that size discovered so far.

HLX-1 brightens and fades roughly once a year. A possible explanation is that the disk of gas is fed by a star in a stretched-out orbit. When the star comes close, the black hole pulls gas from its surface. The gas funnels into the disk, creating a burst of X-rays. The black hole then swallows some of the gas, so the disk fades.

The black hole may be surrounded by a cluster of stars. That could mean that the whole group was originally the core of a small galaxy. The large galaxy it orbits today stripped away its outer regions — leaving a hungry black hole that’s slowly eating one of the galaxy’s few remaining stars.

Script by Damond Benningfield, Copyright 2012

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